It’s been more than two decades since the members of shock-metal group Slipknot first donned their horrific masks, and in that time they’ve become scene leaders. Their two most recent albums, 2008’s All Hope Is Gone and 2014’s .5: The Gray Chapter, both reached Number One on the Billboard 200 and they’ve earned a streak of gold and platinum plaques along the way.

But, even as they have ascended to a level where they can play arenas and stage their own Knotfest, there are still dark corners of their history. Here are five interesting facts about the ensemble – including a record that was never released to the mainstream, a special effigy the group made in tribute to late bassist Paul Gray in the studio and a secret connection the nontet has with another nine-piece group, Bruce Springsteen’s E Street Band – that are not widely known.